Stain resistant melt colored carpet fibers are manufactured by treating nylon fibers with stain protectors.
U.S. Pat. No. 4,822,373 discloses a fibrous polyamide substrate, which has resistance to staining by acid colorants by treatment with a partially sulfonated novolak resin and polymethacrylic acid, copolymers of methacrylic acid, or combination of polymethacrylic acid and copolymers of methacrylic acid.
U.S. Pat. No. 4,940,757 discloses a stain resistant composition, prepared by polymerizing a .alpha.-substituted acrylic acid in the presence of a sulfonated aromatic formaldehyde condensation polymer.
Another method to improve the stain resistance of nylon is to copolymerize nylon with aromatic sulfonates or their alkali metal salts.
U.S. Pat. No. 3,846,507 discloses a process for producing a fiber forming polyamide with reduced acid dye affinity by producing a polymer having certain benzene sulphonate units and then blending it with normal polyamide.
U.S. Pat. No. 4,374,641 discloses a color concentrate for coloring thermoplastic polymeric materials, which is prepared from a blend of a water-dispersable polymer like a polyamide containing benzene sulphonate and a coloring agent.
U.S. Pat. No. 4,579,762 discloses a carpet which is made from fibers of nylon 66 or nylon 6, modified to contain aromatic sulfonate units in an amount sufficient to improve the acid dye-resist properties.
U.S. Pat. No. 5,108,684 discloses a process for producing stain-resistant, pigmented nylon fibers by adding pigment to nylon copolymers containing 0.25-4.0 percent by weight of an aromatic sulfonate or an alkali metal salt thereof.
Disadvantage of the stain resistant fibers described above is, that after a treatment with a high pH shampoo, the stain protection of the fibers, treated with stain protectors is almost disappeared and the stain protection of the sulfonated nylons which have not been treated with stain protectors is decreased.
Object of the present invention was, to provide a process for the manufacture of a stain resistant melt colored carpet, which keeps a high degree of stain protection even after several treatments with a high pH shampoo.